Such a molding track as well as a process for laying carpet and applying a carpet-molding-trim has been described by us in German Offenlegungschrift (open patent application) DE-OS No. 3429715.
This molding trim has proved to be a trail blazing innovation and has produced excellent results. Nevertheless, it possesses a number of disadvantages, which have now been eliminated through further inventive measures.
This earlier molding track requires for reliable adhesion to uneven wall surfaces elaborate fastening devices, which must be coated with adhesive material or be suitable for the application of an adhesive coating.
In order to obtain the desired elastic properties of the molding track, the two lips are constructed with a cross section which narrows toward the top. These two conditions require an extremely complicated profile with a wide variation in the individual cross sections.
The manufacture of this molding track by extrusion requires, therefore, on the one hand correspondingly complex and elaborate extruding tools. On the other hand, the manufacturing process must be very carefully overseen in order to avoid an excessive reject rate due to the differing wall thicknesses.
In addition, making such a profile requires high quality raw materials. So called recycled plastic or synthetic resin made from waste materials of varying composition would lead in this case to an excessively high rejection rate.
A further drawback of the fastening devices is the space they take up, so that only a relatively narrow strip of the molding trim can be clamped in between the wall and front lip. This can, under certain circumstances, lead to unsatisfactory retention of the trim strip and requires, in addition, a narrower tolerance in the width of the trimming strip. Moreover, sliding of the molding trim in between the front lip and the topmost part of the fastening device is made more difficult by the non-streamlined, boxy form of the latter.
Application of the adhesive to the fastening surface requires close attention, in spite of which a considerable amount of the adhesive material makes its way into the spaces between the fastening devices, leading to a wasteful increase in consumption of adhesive material.
Because of the springy elastic behavior of the fastening devices, the additional securing of the molding track by means of nails provided for optionally requires both greater dexterity and a high quality of plastic material in order to prevent splintering of the rear lip and fastening device under the blows of the hammer. If a molding track must be nailed fast at another position at which there happens to be no passage hole, a corresponding hole must be bored here at a precisely measured position in order to avoid damage to the fastening device.
The corners and hollow spaces of the molding track provided for laying electrical wiring are no longer accessible after the molding track has been mounted; hence an initial electrical installation can no longer be changed.